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Avalanche Forecast

Archived

Dec 26th, 2020–Dec 27th, 2020

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Banff Yoho Kootenay.

While more settled weather is on the way, recent winds and snowfall have left a complex snowpack that features a  great deal of variability and multiple weak layers.

There is a Special Avalanche Warning in effect. Click Here to access.

Happy Holidays!

Weather Forecast

After continued light snowfall favoring the northern part of the region, expect some short-lived clearing on Sunday as a ridge develops. Weak disturbances may bring trace amounts of snow Monday and cloud. Alpine winds will remain light out of the west and temperatures near -10C.

Snowpack Summary

Small amounts of new snow now bury wind slabs created by recent 25-45km/hr SW-W winds redistributing the 30-60cm of snow from the past week. The Dec 13 and Dec 7 sun crust/surface hoar/facet layers are down ~ 50cm and ~80 cm respectively. The decomposing Nov crust/facets sits at the bottom of the snowpack. Height of snow at tree line is 120-170cm.

Avalanche Summary

Four days of avalanche control earlier this week produced mixed results, from no result to size 3.0. Most were storm slabs, sometimes stepping down to persistent layers. No new reports or observations today however visibility was limited by snowfall.

Confidence

Due to the number of field observations

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.